The invention generally relates to electro-optics, and more specifically relates to analysis and control of trains of high speed multi-level optical pulses.
Initially, even simple trains of high speed, high power LASER pulses could only be generated by specially trained technicians utilizing a room full of complex and specialized laboratory equipment.
Various factors such as changes in ambient temperature, drift of LASER bias voltages, variations in optical assemblies, and the like cause changes in optical intensity of such trains of high speed, high power LASER pulses, resulting in deviations from a desired optical intensity level.
It may be possible to monitor the optical intensity of such trains of high speed, high power LASER pulses using previously known arrangements, such as extremely high speed sample and hold circuits, peak detectors employing extremely high speed operational amplifiers and diodes, and the like. While these arrangements provide some advantages, they are typically relatively complex, expensive, and difficult to manufacture, use and maintain.
Today, because of mass production and mass merchandising of consumer electronic devices such as readable/re-writeable Compact Disc (CD) drives and the like, ordinary people can generate a train of high speed, high power multi-level LASER pulses within an area less then five and one quarter inches wide (of course, most such people are unaware that they are doing so.)
Write operations typically require that write pulses within the pulse train last for only approximately sixteen to approximately eight nanoseconds or less and have high optical intensity levels of approximately thirty to approximately one hundred milliwatts or more. Similarly, erase operations typically require that erase pulses within the pulse train last for approximately one hundred and fourteen to approximately forty-five nanoseconds or less. However, the erase operations typically require that the erase pulses within the pulse train have a medium optical intensity levels (less than the high optical intensity levels of the write pulses) limited to approximately half of the write pulse intensity, or approximately fifteen to approximately fifty milliwatts or more. Duration of the erase pulse is much longer than duration of the write pulse. For example, duration of the erase pulse is typically approximately forty nanosecond to appoximately four hundred nanoseconds.
Of course, such trains of multi-level pulses are likewise subject to various factors that cause changes from desired optical intensity levels. However, any such trains of multi-level pulses would be even more difficult to monitor than the simple pulses, using the previously known arrangements already discussed herein.
What is needed for consumer electronic devices is a relatively simple (and relatively easy to manufacture, use and maintain) apparatus and method for automatically analyzing and controlling intensity of a train of high speed, high power multi-level optical pulses.
The invention provides a relatively simple (and relatively easy to manufacture, use and maintain) apparatus and method for automatically analyzing and controlling intensity of a train of high speed, high power multi-level optical pulses. These aspects of the invention make it particularly advantageous for use in consumer electronics devices such as readable/re-writeable Compact Disc (CD) drives and the like.
Briefly and in general terms the invention includes an optical pulse generator for generating the train of high speed, high power, multi-level optical pulses, wherein the optical pulse generator provides a low optical intensity level and a medium optical intensity level and a high optical intensity level. A photodetector is optically coupled with the optical pulse generator for generating a train of electrical pulses having amplitude levels in response to optical intensity levels of the train of optical pulses. At least one reference is employed, wherein an analyzer electrically coupled with the reference and the photodetector for analyzing the amplitude levels of the train of electrical pulses in comparison to the reference. A controller is electrically coupled with the analyzer for generating a high correction signal based upon the analysis of the amplitude levels. The controller is coupled with the optical pulse generator for automatically controlling the high optical intensity level of the optical pulse generator based upon the high correction signal.
Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.